Chem 1412 Final Exam. Student:

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1 Chem 1412 Final Exam Student: 1. The radiochemist, Will I. Glow, studied thorium-232 and found that moles emitted α particles in one year. What is the decay constant for thorium-232? A yr -1 B yr -1 C yr -1 D yr -1 E. none of these choices is correct 2. The isotopes of promethium, and, are unstable, and lie on opposite sides of the "line of stability". Which of the following combinations is most likely to represent the type of decay for these isotopes? A. promethium-144, β decay; promethium-134, positron decay B. promethium-144, positron decay; promethium-134, β decay C. promethium-144, positron decay; promethium-134, electron capture D. promethium-144, electron capture; promethium-134, positron decay E. promethium-144, β decay; promethium-134, γ decay 3. Carbon-14 will emit a β particle with an energy of MeV. What is this energy in joules? A J B J C J D J E. none of these choices is correct 4. Which of the following isotopes is most likely to be unstable? A. B. C. D. E.

2 5. Iodine-131, t 1/2 = 8.0 days, is used in diagnosis and treatment of thyroid gland diseases. If a laboratory sample of iodine-131 initially emits β particles per day, how long will it take for the activity to drop to β particles per day? A. 2.0 days B. 16 days C. 32 days D. 128 days E. none of these choices is correct 6. Select the nuclide that completes the following nuclear reaction. A. B. C. D. E. 7. Select the nuclide that completes the following nuclear reaction. A. B. C. D. E. none of these choices is correct 8. A scintillation counter A. measures the signal coming from an ionized gas. B. measures light emissions from excited atoms. C. depends on an avalanche of electrons generated as a particle moves through a tube of argon gas. D. detects high energy radiation better than low energy radiation. E. detects an electric current in a gas.

3 9. Palladium-107 undergoes β decay (t 1/2 = yr) to form silver-107. How long will it take for mol of silver-107 to form from 1.25 mol of palladium-107? A y B y C y D y E y 10. Select the nuclide that completes the following nuclear reaction. A. B. C. D. E. 11. A voltaic cell prepared using zinc and iodine has the following cell notation. Zn(s) Zn 2+ (aq) I - (aq) I 2 (s) C (graphite) Which of the following equations correctly represents the balanced, spontaneous, cell reaction? A. 2I - (aq) + Zn 2+ (aq) I 2 (s) + Zn(s) B. I 2 (s) + Zn(s) 2I - (aq) + Zn 2+ (aq) C. 2I - (aq) + Zn(s) I 2 (s) + Zn 2+ (aq) D. I 2 (s) + Zn 2+ (aq) 2I - (aq) + Zn(s) E. None of these, since graphite must be in the equation. 12. Consider the reaction of iodine with manganese dioxide 3I 2 (s) + 2MnO 2 (s) + 8OH - (aq) 6I - (aq) + 2MnO 4 - (aq) + 4H 2 O(l) The equilibrium constant for the overall reaction is Calculate E cell for the reaction at 25 C. A V B V C V D V E. none of these choices is correct

4 13. Which of the following elements could be prepared by electrolysis of the aqueous solution shown? A. sodium from Na 3 PO 4 (aq) B. sulfur from K 2 SO 4 (aq) C. oxygen from H 2 SO 4 (aq) D. potassium from KCl(aq) E. nitrogen from AgNO 3 (aq) 14. A voltaic cell consists of a Hg/Hg 2 2+ electrode (E = 0.85 V) and a Sn/Sn 2+ electrode (E = V). Calculate [Sn 2+ ] if [Hg 2 2+ ] = 0.24 M and E cell = 1.04 V at 25 C. A M B M C M D M E M 15. A concentration cell consists of two Al/Al 3+ electrodes. The electrolyte in compartment A is M Al(NO 3 ) 3 and in compartment B is 1.25 M Al(NO 3 ) 3. What is the voltage of the cell at 25 C? A V B V C V D V E. none of these choices is correct 16. Calculate ΔG for the combustion of propane. C 3 H 8 (g) + 5O 2 (g) 3CO 2 (g) + 4H 2 O(g) Substance: C 3 H 8 (g) O 2 (g) CO 2 (g) H 2 O(g) ΔG f (kj/mol): A kj B kj C kj D kj E kj

5 17. A certain process has ΔS univ > 0 at 25 C. What does one know about the process? A. It is exothermic. B. It is endothermic. C. It is spontaneous at 25 C. D. It will move rapidly toward equilibrium. E. none of these choices is correct 18. Which relationship or statement best describes ΔS for the following reaction? BaCl 2 (aq) + Na 2 SO 4 (aq) BaSO 4 (s) + 2NaCl(aq) A. ΔS 0 B. ΔS < 0 C. ΔS > 0 D. ΔS = ΔH /T E. More information is needed to make a reasonable prediction. 19. Use the thermodynamic data at 298 K below to determine the K sp for barium carbonate, BaCO 3 at this temperature. Substance: Ba 2+ (aq) CO 2-3 (aq) BaCO 3 (s) ΔH f (kj/mol): ΔG f (kj/mol): S (J/K mol): A B C D E For a chemical reaction to be spontaneous at all temperatures, which of the following conditions must be met? A. ΔS > 0, ΔH > 0 B. ΔS > 0, ΔH < 0 C. ΔS < 0, ΔH < 0 D. ΔS < 0, ΔH > 0 E. It is not possible for a reaction to be spontaneous at all temperatures.

6 21. Which of the following substances has the greatest solubility in water? A. MgCO 3, K sp = B. NiCO 3, K sp = C. AgIO 3, K sp = D. CuBr, K sp = E. AgCN, K sp =

7 22. Which one of the following is the best representation of the titration curve which will be obtained in the titration of a weak base (0.10 mol L -1 ) with HCl of the same concentration? A. B. C. D. E.

8 23. When a strong acid is titrated with a weak base, the ph at the equivalence point A. is greater than 7.0. B. is equal to 7.0. C. is less than 7.0. D. is equal to the pk a of the acid. E. is equal to the pk b of the base. 24. The solubility of silver chromate is g/1.0 L of solution. What is the K sp for Ag 2 CrO 4? A B C D E. < Equal volumes of the following pairs of solutions are mixed. Which pair will produce a buffer solution? A mol L -1 HCl and 0.05 mol L -1 NaOH B mol L -1 HCl and 0.15 mol L -1 NH 3 C mol L -1 HCl and 0.05 mol L -1 NH 3 D mol L -1 HCl and 0.20 mol L -1 CH 3 COOH E mol L -1 HCl and 0.20 mol L -1 NaCl 26. The substance NaNO 3 is considered A. a weak Arrhenius acid. B. a weak Arrhenius base. C. a strong Arrhenius acid. D. a strong Arrhenius base. E. a neutral compound. 27. A 0.15 M solution of chloroacetic acid has a ph of What is the value of K a for this acid? A B C D E

9 28. Which one of the following will give a solution with a ph > 7, but is not an Arrhenius base in the strict sense? A. CH 3 NH 2 B. NaOH C. CO 2 D. Ca(OH) 2 E. CH Which of the following is a Lewis base? A. BCl 3 B. Cu 2+ C. Cl - D. Mn 2+ E. NH Which of the following aqueous liquids is the most acidic? A. 0.1 M Al(NO 3 ) 3, K a = B. 0.1 M Be(NO 3 ) 2, K a = C. 0.1 M Pb(NO 3 ) 2, K a = D. 0.1 M Ni(NO 3 ) 2, K a = E. pure water 31. At 25 C, the equilibrium constant K c for the reaction 2A(aq) B(aq) + C(aq) is 65. If 2.50 mol of A is added to enough water to prepare 1.00 L of solution, what will the equilibrium concentration of A be? A M B M C M D M E. 2.4 M

10 32. Ammonium iodide dissociates reversibly to ammonia and hydrogen iodide. NH 4 I(s) NH 3 (g) + HI(g) At 400 C, K p = Calculate the partial pressure of ammonia at equilibrium when a sufficient quantity of ammonium iodide is heated to 400 C. A atm B atm C atm D atm E atm 33. A mixture of mol of bromine and mol of iodine is placed into a rigid L container at 350 C. Br 2 (g) + I 2 (g) 2IBr(g) When the mixture has come to equilibrium, the concentration of iodine monobromide is M. What is the equilibrium constant for this reaction at 350 C? A B C D. 282 E Compounds A, B, and C react according to the following equation. 3A(g) + 2B(g) 2C(g) At 100 C a mixture of these gases at equilibrium showed that [A] = M, [B] = 1.23 M, and [C] = 1.75 M. What is the value of K c for this reaction? A B C D E. > 10

11 35. Consider the equilibrium reaction: H 2 (g) + Br 2 (g) 2HBr(g) Which of the following correctly describes the relationship between K c and K p for the reaction? A. K p = K c B. K p = (RT)K c C. K p = (RT) 2 K c D. K p = K c /RT E. K p = K c /(RT) When the reaction A B + C is studied, a plot of ln[a] t vs. time gives a straight line with a negative slope. What is the order of the reaction? A. zero B. first C. second D. third E. More information is needed to determine the order. 37. Consider the following mechanism for the oxidation of bromide ions by hydrogen peroxide in aqueous acid solution. H + + H 2 O 2 H 2 O + -OH (rapid equilibrium) H 2 O + -OH + Br - HOBr + H 2 O (slow) HOBr + H + + Br - Br 2 + H 2 O (fast) Which of the following rate laws is consistent with the mechanism? A. Rate = k[h 2 O 2 ][H + ] 2 [Br - ] B. Rate = k [H 2 O + -OH][Br - ] C. Rate = k[h 2 O 2 ][H + ][Br - ] D. Rate = k[hobr][h + ][Br - ][H 2 O 2 ] E. Rate = k[br - ] 38. Ammonia will react with oxygen in the presence of a copper catalyst to form nitrogen and water. From C to C, the rate constant increases by a factor of What is the activation energy of this oxidation reaction? A kj/mol B. 165 kj/mol C. 242 kj/mol D kj/mol E. > 10 4 kj/mol

12 39. A study of the decomposition reaction 3RS 2 3R + 6S yields the following initial rate data [RS 2 ](mol L -1 ) Rate (mol/(l s)) What is the rate constant for the reaction? A L mol -1 s -1 B L mol -1 s -1 C L mol -1 s -1 D L mol -1 s -1 E L mol -1 s NOBr(g) 2NO(g) + Br 2 (g) [NOBr](mol L -1 ) Rate (mol L -1 s -1 ) Based on the initial rate data above, what is the value of the rate constant? A L mol -1 s -1 B L mol -1 s -1 C L mol -1 s -1 D L mol -1 s -1 E s How many moles of sulfate ions are present in 1.0 L of 0.5 M Li 2 SO 4? A. 0.5 mol B. 1.0 mol C. 1.5 mol D. 2.0 mol E. 3.0 mol 42. Two aqueous solutions are prepared: 1.00 m Na 2 CO 3 and 1.00 m LiCl. Which of the following statements is true? A. The Na 2 CO 3 solution has a higher osmotic pressure and higher vapor pressure than the LiCl solution. B. The Na 2 CO 3 solution has a higher osmotic pressure and higher boiling point than the LiCl solution. C. The Na 2 CO 3 solution has a lower osmotic pressure and lower vapor pressure than the LiCI solution. D. The Na 2 CO 3 solution has a lower osmotic pressure and higher boiling point than the LiCl solution. E. None of these statements is true.

13 43. A solution of sucrose (sugar) in water is in equilibrium with solid sucrose. If more solid sucrose is now added, with stirring, A. the concentration of the solution will increase. B. the concentration of the solution will decrease. C. the concentration of the solution will remain the same. D. the volume of solution will increase. E. a supersaturated solution will be produced. 44. What volume of concentrated (14.7 M) phosphoric acid is needed to prepare 25.0 L of 3.0 M H 3 PO 4? A L B L C. 1.8 L D. 3.6 L E. 5.1 L 45. Colligative properties depend on A. the chemical properties of the solute. B. the chemical properties of the solvent. C. the masses of the individual ions. D. the molar mass of the solute. E. the number of particles dissolved. 46. Which of the following should have the lowest boiling point? A. C 5 H 12 B. C 6 H 14 C. C 8 H 18 D. C 10 H 22 E. C 12 H Select the pair of substances in which the one with the higher vapor pressure at a given temperature is listed first. A. C 7 H 16, C 5 H 12 B. CCl 4, CBr 4 C. H 2 O, H 2 S D. CH 3 CH 2 OH, CH 3 -O-CH 3 E. Xe, Kr

14 48. Octane has a vapor pressure of 40. torr at 45.1 C and 400. torr at C. What is its heat of vaporization? A kj/mol B kj/mol C. 590 kj/mol D. 710 kj/mol E. none of these choices is correct 49. Which of the following is true about kinetic energy, E k, and potential energy, E p, when ethyl alcohol at 40 C is compared with ethyl alcohol at 20 C? A. E k (40 C) < E k (20 C); E p (40 C) E p (20 C) B. E k (40 C) > E k (20 C); E p (40 C) E p (20 C) C. E p (40 C) < E p (20 C); E k (40 C) E k (20 C) D. E p (40 C) > E p (20 C); E k (40 C) E k (20 C) E. E p (40 C) > E p (20 C); E k (40 C) > E k (20 C) 50. A sample of octane in equilibrium with its vapor in a closed 1.0-L container has a vapor pressure of 50.0 torr at 45 C. The container's volume is increased to 2.0 L at constant temperature and the liquid/vapor equilibrium is reestablished. What is the vapor pressure? A. > 50.0 torr B torr C torr D. The mass of the octane vapor is needed to calculate the vapor pressure. E. The external pressure is needed to calculate the vapor pressure.

15 Chem 1412 S06 Final Exam Key 1. (p. 1054) B 2. (p. 1051) A 3. (p. 1071) D 4. (p. 1051) B 5. (p. 1056) C 6. (p. 1048) A 7. (p. 1049) A 8. (p. 1055) B 9. (p. 1056) E 10. (p. 1049) D 11. (p. 912) B 12. (p. 925) D 13. (p. 944) C 14. (p. 927) C 15. (p. 930) D 16. (p. 884) A 17. (p. 870) C 18. (p. 871) B 19. (p. 892) C 20. (p. 887) B 21. (p. 837) B 22. (p. 830) D 23. (p. 830) C 24. (p. 835) C 25. (p. 816) B 26. (p. 772) E 27. (p. 783) D 28. (p. 772) A 29. (p. 801) C

16 30. (p. 795) A 31. (p. 739) B 32. (p. 739) D 33. (p. 738) D 34. (p. 738) D 35. (p. 734) A 36. (p. 688) B 37. (p. 703) C 38. (p. 693) B 39. (p. 685) E 40. (p. 685) B 41. (p. 525) A 42. (p. 525) B 43. (p. Sec. 13.4) C 44. (p. 510) E 45. (p. 515) E 46. (p. Sec. 12.3) A 47. (p. Sec. 12.3) B 48. (p. 432) A 49. (p. 429) B 50. (p. 431) B

17 Chem 1412 S06 Final Exam Summary Category # of Questions Difficulty: E 17 Difficulty: H 10 Difficulty: M 23

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